The invention relates to an electric incancescent lamp comprising:
a moulded glass plate which is connected in a gastight manner to current conductors and to a metal tube which extend through said plate;
an incandescent body occupying a predetermined position relative to the moulded plate and connected to the current conductors;
a glass bulb around the incandescent body, connected in a gastight manner to the moulded plate by means of enamel;
a filling gas having a pressure of at least 1 bar inside the bulb,
said metal tube having a gastight seal outside the bulb.
Such an electric incandescent lamp is known from FR-B-913,579.
The known lamp has a moulded or pressed glass plate with a circular edge with a locating stud thereon. The lamp is designed for being passed with its bulb in front through an opening in a reflector and for being pressed home with the edge of the plate against a boundary of said opening. The reflector with the lamp may be used as a motor vehicle headlamp for generating a passing beam and a driving beam.
It is a disadvantage of the known electric lamp that the glass plate can only be manufactured with wide dimensional tolerances. This means that the position of the incandescent body is also badly defined.
It is desirable in other applications of incandescent lamps, for example at the rear of vehicles such as motor cars, to have available electric incandescent lamps which can be moved backwards, i.e. with a lamp cap or base in front, against a carrier, and whose incandescent body then occupies an accurately defined position relative to this carrier with the bulb facing away from the carrier. Such lamps may be used for the stop light, the tail light, the reversing light, the rear fog lamp, the indicator lights, etc.
Known electric incandescent lamps for these functions are provided with lamp caps. The incandescent body thereof has a position which is defined within no more than wide limits relative to said lamp cap, and the lamps have a comparatively short life. In addition, there is a comparatively high early failure rate owing to lamp leaks.